This invention relates to saddle binding systems and is particularly concerned with a reject device for removing misformed books from the gathering chain of such a system. A misformed book is one that is missing pages, is misaligned or is otherwise unsatisfactory for use.
A saddle binding system is a group of machines which collate individual printed sheets, called signatures, into finished books. The complete layout of such a system is shown in McCain, U.S. Pat. No. 4,384,709. In saddle binding the signatures are folded and placed one atop another with the folds aligned to define a backbone. This is done by a plurality of signature feeders. A signature feeder is shown in McCain, U.S. Pat. No. 4,241,907. Each feeder places a signature on a gathering chain which has pusher pins to advance a group of signatures past each of the feeders. When a book has passed all feeders, a caliper measures the thickness of the book to test whether it contains all signatures. If so, the book is stapled at the backbone. Thereafter the edges of the book are trimmed and a mailing label may be attached and books may be grouped or tied for shipment.
Occasionally, a signature feeder may fail to properly add its signature to a passing book. Sensors in the signature feeder can detect a misfeed and provide a signal successively to disable downstream feeders when the misformed book arrives at each one. This limits the amount of signatures that are placed on books that are known to be bad. Since the signatures are valuable enough to warrant recycling them from misformed books, the downstream shutoff feature limits the amount of work involved in separating and recycling signatures from misformed books.
Regardless of whether downstream shutoff is used, the stitcher will be disabled so as not to stitch a bad book. The stitcher, however, is set up to handle fully-formed books. Books that vary substantially from the desired thickness have an increased likelihood of jamming the stitcher. Use of the downstream shutoff feature can produce such books. For example, if a misfeed occurs at the fifth feeder of a system with twenty feeders, the downstream shutoff will disable feeders six through twenty from feeding to the bad book. However, the misformed book having only four or five of the expected twenty signatures continues moving with the gathering chain toward the stitcher. The caliper will disable the wire feed of the stitcher heads so the book will not be bound. But the gripper bar that advances books through the stitcher may not be able successfully to grip the thin book and move it through the stitcher.
One possible solution to this problem is to forego the benefits of downstream shutoff. This increases the labor involved in recycling signatures. Another solution is to remove misformed books from the gathering chain before they reach the stitcher area. That is the approach of this invention. However, the high speed of present-day saddle binding systems makes book removal a complex problem. These systems can produce books at a rate of about five books per second. So on average, about a fifth of a second is available between successive books reaching a particular point on the conveyor. This short book cycle leaves very little time to alter the normal course of a book. A further complicating factor is that the removed signatures must be handled carefully so they come out in a reusable condition.